Summary

Assays for the succinoxidase and oxalacetic acid oxidase systems were carried out on the livers of rats that had received a stock grain diet, a basal diet containing 12 per cent casein, or the latter diet containing the 2-methyl, 2′-methyl, 3′-methyl, or 4′-fluoro derivatives of 4-dimethylaminoazobenzene or 3-methyl-4-monomethylaminoazobenzene for periods of 4–6 weeks. In addition, the 3′-methyl compound was fed for shorter periods to determine the time course of the changes in the case of this compound.

The results were compared with the analyses for intracellular components reported in the accompanying paper, and the succinoxidase values were found to correlate most clearly with the values for mitochondrial protein, in accordance with the fact that the enzyme is localized in the mitochondria.

The succinoxidase values decreased with increasing carcinogenicity within the C-monomethyl series of derivatives but did not decrease significantly with the strongly carcinogenic 4′-fluoro derivative within the period studied.

The succinoxidase values increased to more than double the control values in the case of the 2-methyl derivative, but the oxalacetic acid oxidase enzyme system was not increased in the same samples.

The results support the view that the synthesis or multiplication of the mitochondria proceeds independently of cell multiplication, and were discussed in relation to the enzyme-deletion hypothesis of cancer formation.

Footnotes

↵* This work was supported by grants from the American Cancer Society on recommendation of the Committee on Growth of the National Research Council, and the National Cancer Institute. We are indebted to Mrs. Gloria G. Lyle for technical assistance in the enzyme assays.